This is slightly off the main topic (the heat), but have you tried feeding rats?
in my experience, (though i'm far from an expert) i've had better luck
in general feeding one good sized meal every three to four weeks.

Sometimes they don't make the switch from mice to rats, and then, you do what you have to....but if you haven't, maybe giving that a shot might help him/her out in the long run. I would think you'd save some money too, not having to feed every week.
3 adult mice would probably equal at least a medium rat, (someone please correct me if I'm wrong ) and you could try feeding every other week until the snake is used to the change.

just my .